Room temperature two-part vulcanizing silicone compositions are presently widely known. For example, Hyde, U.S. Pat. No. 2,571,039 discloses preparing an organosiloxane by compounding a readily deformable acid polymer comprising a polysiloxane and an acidic compound with a filler, and then reacting the compounded material with a silane of the formula R.sub.n Si(OR').sub.4-n where R is a monovalent hydrocarbon radical free of aliphatic unsaturation, R' is an alkyl radical of less than 9 carbon atoms and n has a value of 0 to 1.
Berridge, United States Patent No. 2,843,555 discloses an organopolysiloxane composition convertible at room temperature to the cured, solid, elastic state comprising (a) a linear, fluid organopolysiloxane containing silicon-bonded hydroxy groups and having an average of about two organic groups per silicon atom, (b) an alkyl silicate, and (c) a metallic salt of an organic carboxylic acid.
The compositions are useful as sealants, electrical insulation, coatings, dental cement, caulking compounds, expansion joints, gaskets, shock absorbers, adhesives and in many other applications.
Presently, two-part condensation cure RTV's are typically comprised of an "A" component comprising (1) a dihydroxy or silanol terminated polydiorganosiloxane; (2) a semi-reinforcing filler such as CaCO.sub.3 or ground quartz and a reinforcing filler such as fumed silica; and (3) water; and a "B" component comprising (1) a T or Q functional crosslinker; and (2) a condensation cure catalyst.
It is further known in the art to treat the fillers off site with organosilicones or silazanes prior to addition to the two component RTV mixture. See, for example, Lucas, U.S. Pat. Nos. 2,938,009; Lichtenwalner, 3,004,859; and Smith, 3,635,743.
More recently, Treco SRL has developed a low shear process for treating the filler in situ by preparing a filler/oil masterbatch and adding the treating agent to the masterbatch under low shear mixing conditions which do not rapidly break down aggregated filler particles. Although the Treco process has met with some success in the industry, the process requires unsuitable manufacturing times, on the order of at least about 3 to 5 days. Further, materials produced by the Treco process exhibit relatively low Shore A durometer and Die B Tear values.
It would therefore represent a notable advance in the state of the art if a novel method could be found which enabled a user to treat the filler in situ and formulate a two component RTV composition in a significantly shorter manufacturing time to produce a high Shore A durometer material which retained high Die B Tear values.